The present invention relates generally to a data recording apparatus, data recording method, and data transfer system which are suitable in transferring/recording content data such as music.
A usage form is available in which content data such as music are stored in a primary recording medium such as a HDD (Hard Disc Drive) of a personal computer and the stored content data are transferred/recorded to another recording medium (a secondary recording medium) for the reproduction of music on the side of the secondary recording medium, for example. The content data herein denote main data such as music data, image data, game data, and computer software which are subject to distribution/transfer/use. Alternatively, the content data may be either with or without compression.
In this case, the HDD stores the content data such as music reproduced from a package medium such as CD-DA (Compact Disc Digital Audio) and DVD (Digital Versatile Disc) and the content data downloaded from an external music server for example via a communication network to which a personal computer concerned is connected. By connecting the personal computer to the recording apparatus, which is the secondary recording medium, the user of the computer copies, or moves the content data from the HDD to the secondary recording medium to reproduce the content data such as music by a reproducing apparatus compatible with this secondary recording medium.
The secondary recording medium may include a memory card based on the semiconductor memory such as a flash memory, a MiniDisc, which is a magneto-optical disc, a CD-R (CD Recordable), a CD-RW (CD Rewitable), a DVD-RAM, a DVD-R, and a DVD-RW for example.
The recorders/players compatible with these media as the recording apparatus and reproducing apparatus for the secondary recording media are in wide use and available in a variety of manners as stationary or portable recording/reproducing apparatuses. Each user can record/reproduce desired content data in accordance with user's preferences or devices.
It should be noted that, if content data are used in any of the above-mentioned manners, the copyright protection of these content data must be taken into account. For example, if the user is allowed to store content data into the HDD by use of a content data distribution service or by purchase of a package medium and then copy the stored content data absolutely into a secondary recording medium, the proper protection of copyright holders of these content data may be violated. In order to prevent this problem from happening, several arrangements have been proposed in the technologies and data processing for maintaining the copyright protection in handling content data as digital data. One of these arrangements is the SDMI (Secure Digital Music Initiative) standard. The data path formulated in the SDMI standard will be described later. For example, the data path is designed in consideration of both copyright protection and general user benefit (the right of duplication for private use) to properly perform the transfer/recording of the content stored in a personal computer having a HDD as the primary recording medium, for example the content data distributed from an external server via a network (hereafter referred to as network content) and the content data retrieved from the package media such as CD-DA and DVD which are reproduced on a disc drive unit such as a CD-ROM drive mounted on a personal computer or a disc drive unit which is externally connected to a personal computer (hereafter referred to as disc content).
In order to satisfy the requirements of both copyright and private duplication right in transferring content data from the primary recording medium such as HDD to the secondary recording medium such as MiniDisc for copying, a content data transfer method is proposed in which a data transfer apparatus (a device on the primary recording medium side) authenticates a data recording apparatus to be transferred (a device on the secondary recording medium side) and, only when the authentication is successful, the data transfer apparatus transfers content data to the data recording apparatus, the content data are transferred in an encrypted state, and the data recording apparatus decrypts the encrypted content data before recording.
A method of content data encryption and decryption is as follows for example. Assume that content data to be downloaded from an external server and stored in a HDD, which is the above-mentioned primary recording medium, are encrypted by content key CK. For the purpose of description, it is assumed that the HDD, which is the primary recording medium, stores content data “A3D” compressed by ATRAC3 (or any other data compression algorithm) and encrypted by content key CK.
It should be noted herein that, for the purpose of description, data y encrypted by a key x are expressed in E(x, y) and data decrypted by the key x from encrypted data E(x, y) are expressed in D{x, E(x, y)}.
Consequently, let the data compressed by ATRAC3 be “A3D” as shown above, then content data “A3D” encrypted by a content key CK are expressed in E(CK, A3D). If the data decrypted by the key CK from E(CK, A3D) are expressed in D{CK, E(CK, A3D)}.
The HDD, which is the primary recording medium, also stores the content key CK encrypted by a root key KR, namely E(KR, CK), along with encrypted content data E(CK, AD). For example, the encrypted content key E (KR, CK) is downloaded from an external server along with encrypted content data E(KR, A3D).
In this case, when transferring content data from the HDD, which is the primary recording medium, to the secondary recording medium, encrypted content data E(CK, A3D) and encrypted content data key E(KR, CK) may be transmitted.
The device on the secondary recording medium holds a root key KR, so that the device can decrypt the content key CK by use of the root key KR and then decrypt encrypted content data by the decrypted content key CK.
However, the root key KR is subject to change depending on the intention of copyright holder or other situations and therefore different root keys KR may be set to different pieces of content data. Also, the destinations of content distribution may be restricted by root key KR processing, a specific example of which will be described later.
For this purpose, data called an enabling key block (EKB) may be distributed. Each authorized terminal to which content data are transferred employs a method in which the root key can be confirmed by an EKB. Namely, an EKB is also distributed from a server along with the above-mentioned encrypted content data and encrypted content key and stored in the HDD.
In the above-mentioned circumstances, when transferring content data from the primary recording medium such as HDD to the secondary recording medium such as MiniDisc for copying, steps as shown in FIGS. 1A and 1B is taken as transfer processing.
FIG. 1A shows an example in which one piece of content data is transferred from a HDD to a MiniDisc to record the transferred content data thereto.
First, in step c1, the device on the primary recording medium side incorporating a HDD authenticates the device on the secondary recording medium side, which is a MiniDisc recording apparatus.
If the authentication is successful, then, in step c2, the device on the primary recording medium side performs the confirmation of the root key KR. Namely, the device on the primary recording medium side sends the EKB associated with the content data to be transmitted to the device on the secondary recording medium side to allow the same to determine the root key KR.
Next, in step c3, the device on the primary recording medium side sends the encrypted content key CK to the device on the secondary recording medium side. The device on the secondary recording medium side decrypts the encrypted content key CK by the above-mentioned confirmed root key KR.
In step c4, the device on the primary recording medium side sends the encrypted content data to the device on the secondary recording medium side. The device on the secondary recording medium side decrypts the encrypted content data by the above-mentioned decrypted content key CK, performs predetermined data processing on the decrypted content data, and records the resultant content data to the MiniDisc, which is the secondary recording medium.
Finally, in step c5, the device on the secondary recording medium updates management information known as U-TOC on the MiniDisc along with the writing of the content data thereto, upon which this recording operation is completed.
By following the above-mentioned steps, one piece of content data can be transferred/copied for recording while protecting its copyright.
FIG. 1B shows the recording of three pieces of content data by continuously transferring them from a HDD to a MiniDisc.
In this case, in steps d1 through d5 which are the same as the above-mentioned steps c1 through c5 shown in FIG. 1A, a first piece of content data is transferred and recorded. In steps d6 through d10 which are the same as the above-mentioned steps c1 through c5 shown in FIG. 1A, a second piece of content data is transferred and recorded. In steps d11 through d15 which are the same as the above-mentioned steps c1 through c5 shown in FIG. 1A, a third piece of content data is transferred and recorded.
For example, when transferring/recording two or more pieces of content data as above, the steps shown in FIG. 1A are repeated by the number of pieces of content data to be transferred.